Structural and Tectonic Controls of Geothermal Activity in the Basin and Range Province

We are conducting an inventory of structural settings of geothermal systems (>400 total) in the extensional to transtensional Great Basin region of the western USA. A system of NW-striking dextral faults known as the Walker Lane accommodates ~20% of the North American-Pacific plate motion in the western Great Basin and is intimately linked to N- to NNE-striking normal fault systems throughout the region. Overall, geothermal systems are concentrated in areas with the highest strain rates within or proximal to the eastern and western margins of the Great Basin, with the highest temperature systems clustering in transtensional areas of highest strain rate in the northwestern Great Basin.

Of the 250+ geothermal fields catalogued, step-overs or relay ramps in normal fault zones serve as the most favorable setting, hosting ~32% of the systems. Such areas have multiple, overlapping fault strands, increased fracture density, and thus enhanced permeability. Other common settings include a) intersections between normal faults and strike-slip or oblique-slip faults (22%), where multiple minor faults connect major structures and fluids can flow readily through highly fractured, dilational quadrants, and b) normal fault terminations or tip-lines (22%), where horse-tailing generates closely-spaced faults and increased permeability. Other settings include accommodation zones (i.e., belts of intermeshing, oppositely dipping normal faults; 8%), major normal faults (6%), displacement transfer zones (5%), and pull-aparts in strike-slip faults (4%). In addition, Quaternary faults lie within or near most systems (e.g., Bell and Ramelli, 2007). The relative scarcity of geothermal systems along displacement-maxima of major normal faults may be due to reduced permeability in thick zones of clay gouge and periodic release of stress in major earthquakes. Step-overs, terminations, intersections, and accommodation zones correspond to long-term, critically stressed areas, where fluid pathways are more likely to remain open in networks of closely-spaced, breccia-dominated fractures.

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Additional Info

Field Value
Author University of Nevada
Maintainer James E. Faulds
bureau_code 019:20
Catalog GDR
Contact Phone 775.682.8751
harvest_object_id 43cf26ea-d123-4895-979f-b2f6b16b1111
harvest_source_id 154c8289-1404-4e71-a217-a08000129ad0
harvest_source_title Geothermal Data Repository (GDR)
Origination Date 2012-11-30
program_code 019:006
Sectors Geothermal
was_harvested true

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